Search Publications
Elemental Abundances in the X-Ray Gas of Early-Type Galaxies with XMM-Newton and Chandra Observations
Bregman, Joel N.; Irwin, Jimmy A.; Ji, Jun +2 more
The source of hot gas in elliptical galaxies is thought to be due to stellar mass loss, with contributions from supernova (SN) events and possibly from infall from a surrounding environment. This picture predicts supersolar values for the metallicity of the gas toward the inner part of the galaxy, which can be tested by measuring the gas phase abu…
Titan's induced magnetosphere under non-ideal upstream conditions: 3D multi-species hybrid simulations
Simon, Sven; Motschmann, Uwe
A 3D, multi-species hybrid model (kinetic ions, fluid electrons) has been applied to the interaction between Saturn's largest satellite Titan and the plasma in the giant planet's outer magnetosphere. In contrast to the idealized picture deduced from Voyager 1 data, recent observations made by the Cassini magnetometer instrument suggest that the am…
Long-term photometric monitoring with the Mercator telescope. Frequencies and multicolour amplitudes of γ Doradus stars
Uytterhoeven, K.; Drummond, R.; De Ridder, J. +21 more
Context: γ Dor stars are excellent targets for asteroseismology since the gravity modes present in these stars probe the deep stellar interiors. Mode identification will improve the knowledge of these stars considerably.
Aims: A selected group of γ Dor stars and some candidates were observed with the Mercator telescope to find and/or confirm t…
The XMM-NEWTON Long Look of NGC 1365: Lack of a High/Soft State in its Ultraluminous X-Ray Sources
Bianchi, S.; Elvis, M.; Fabbiano, G. +3 more
Based on our long (~300 ks) 2007 XMM-Newton observation of the Seyfert galaxy NGC 1365, we report here on the spectral and timing behavior of two ultraluminous X-ray sources (ULXs), which had previously reached isotropic X-ray luminosities L X ≈ 4 × 1040 erg s-1 (0.3-10 keV band). In 2007, they were in a lower stat…
Stereoscopic Reconstruction from STEREO/EUV Imagers Data of the Three-dimensional Shape and Expansion of an Erupting Prominence
Bemporad, A.
On 2007 May 9, a prominence eruption was observed in the He II λ304 filter by the two EUV Imagers (EUVI) telescopes aboard the STEREO A and B spacecrafts. The high spatial resolution (~1farcs5 pixel-1) EUVI images have been used to infer via triangulation the three-dimensional (3D) shape and orientation of the prominence sime12 minutes …
HST/ACS colour-magnitude diagrams of M 31 globular clusters
Cacciari, C.; Bellazzini, M.; Galleti, S. +3 more
Aims: With the aim of increasing the sample of M 31 clusters for which a colour-magnitude diagram is available, we searched the HST archive for ACS images containing objects included in the Revised Bologna Catalogue of M 31 globular clusters (RBC Version 3.5 available at: http://www.bo.astro.it/M31).
Methods: Sixty-three such objects were foun…
Deep Keck u-Band Imaging of the Hubble Ultra Deep Field: A Catalog of z ~ 3 Lyman Break Galaxies
Rafelski, Marc; Chen, Hsiao-Wen; Wolfe, Arthur M. +3 more
We present a sample of 407 z ~ 3 Lyman break galaxies (LBGs) to a limiting isophotal u-band magnitude of 27.6 mag in the Hubble Ultra Deep Field. The LBGs are selected using a combination of photometric redshifts and the u-band drop-out technique enabled by the introduction of an extremely deep u-band image obtained with the Keck I telescope and t…
Discovery of X-Ray Emission from the Wolf-Rayet Star WR 142 of Oxygen Subtype
Hamann, W. -R.; Chu, Y. -H.; Oskinova, L. M. +2 more
We report the discovery of weak yet hard X-ray emission from the Wolf-Rayet (WR) star WR 142 with the XMM-Newton X-ray telescope. Being of spectral subtype WO2, WR 142 is a massive star in a very advanced evolutionary stage shortly before its explosion as a supernova or γ-ray burst. This is the first detection of X-ray emission from a WO-type star…
Estimating the Chromospheric Absorption of Transition Region Moss Emission
De Pontieu, Bart; McIntosh, Scott W.; Hansteen, Viggo H. +1 more
Many models for coronal loops have difficulty explaining the observed EUV brightness of the transition region, which is often significantly less than theoretical models predict. This discrepancy has been addressed by a variety of approaches including filling factors and time-dependent heating, with varying degrees of success. Here, we focus on an …
Optical and X-ray Observations of M31N 2007-12b: An Extragalactic Recurrent Nova with a Detected Progenitor?
Shafter, A. W.; Page, K. L.; Bode, M. F. +4 more
We report combined optical and X-ray observations of nova M31N 2007-12b. Optical spectroscopy obtained 5 days after the 2007 December outburst shows evidence of very high ejection velocities (FWHM Hα sime 4500 km s-1). In addition, Swift X-ray data show that M31N 2007-12b is associated with a Super-Soft Source (SSS) which appeared betwe…